This application is a 371 of PCT/JP99/04200 filed Aug. 4, 1999.
1. Field of the Invention
This invention concerns a method of reaction in water catalyzed by Lewis acid. More specifically, this invention relates to a novel method of reaction in water catalyzed by Lewis acid, which carries out organic synthesis reactions using Lewis acid that constitute kerners of not only organic synthesis chemistry but also modern fine organic chemistry such as polymer chemistry and material chemistry, by using water as a part or all of the solvent and under the presence of a Lewis acid which is stable in water.
2. Description of the Related Art
Various organic chemical reactions using general Lewis acids such as AlCl3 or finely designed Lewis acids such as HFxe2x80x94BF3 as the catalyst have been known in experimental method or industrial method (Chemistry and Industry, vol. 50, No. 10 (1997) 1481-1501). Then, organic synthesis for high addition value chemical products such as novel advanced functional compounds, fine chemical products, polymeric compounds for medicinal and agricultural chemicals has become more and more important in recent years, and Lewis acid catalysts have been used generally for the organic synthesis reactions, exhibited their performance in various fields and have been used generally as indispensable catalysts.
On the other hand, development for chemical reactions or processes considering human or global environments has recently been demanded socially, and regulations for organic solvents such as benzene or halogen-containing solvents have become severer year by year, so that synthesis technology of conducting various organic reactions in aqueous solvents has been highlighted and requirement has been increased also in the organic synthesis reactions using the Lewis acid as the catalyst.
However, metal ions from metal compounds used as the Lewis acid mainly include those ions from group IB, group IIB, group IIIB, group IVA, group IVB and group III belonging to the periodical table and, for example, AlCl3 or BF3 from the IIIB group metal as the typical Lewis acid is rapidly hydrolyzed. Further, most of Lewis acids of the metals in each group are rapidly reacted with water and hydrolyzed to be inactivated, so that it has been considered so far that use of the Lewis acid in an aqueous solution is impossible.
However, the inventor of the present application has recently found that rare earth metal trifluoro methane sulfonates (rare earth triflate) are stable also in water and function as the Lewis acid in the aqueous solution (Journal of the Society of Organic Synthesis Chemistry, 53, 370 (1995)). Since the rare earth triflates are dissolved more easily in water than in organic solvents, they can be recovered easily by extraction after the completion of the reaction and the catalytic activity is not lost even by repeated use of several times. However, for such novel finding made by the inventor of the present application, no sufficient study has yet been made as to whether they show appropriate Lewis acid catalytic activity under the reaction conditions in the aqueous system usable industrially or as to whether the reactions can be carried out at a high yield in the aqueous system with regard to the entire Lewis acid, so that an appropriate Lewis acid catalyst has been selected by trial and error. Accordingly, it has been desired to establish general rules or indications for enabling rapid selection therefor.
If the metal compounds including the rare earth triflates described above which are stable also in water and function as the Lewis acid can be defined clearly along the general rules or indications, it will be possible to design a generally applicable, environment-preserving type organic synthesis systems basically free from the requirement for discarding of the catalyst and to expect attainment of organic chemical reactions which use an aqueous solution and which are so to speak gentle to environment. Accordingly, establishment of more comprehensive and generally applicable technology for reactions in water catalyzed by Lewis acid has been an extremely important subject.
This invention of the present application has been achieved in view of the foregoing situations and it is an object thereof to provide a more comprehensive and generally applicable novel method of reaction in water catalyzed by Lewis acid, basically free from the requirement for discarding the catalyst and employing water as a part or all of the solvent, which is gentle to global environments and safe to social environments including human beings.
For solving the subject described above, the invention of the present application provides, at first, a method of reaction in water catalyzed by a Lewis acid for an organic synthesis reaction method by using a metal compound stable in water and functioning as a Lewis acid and employing water as a part or all of a solvent, wherein the hydrolysis constant (pKh) of the metal ion of the metal compound is within a range: 4.3xe2x89xa6pKhxe2x89xa610.1 and the water exchange rate constant (WERC) thereof is 3.2xc3x97106Mxe2x88x921secxe2x88x921 or more, and wherein the metal ion of the metal compound is iron (II) ion, copper (II) ion or lead (II) ion.